Ch. 5: Intensities Flashcards
Spatial refers to…
location, distance or space.
Define ‘peak’.
maximum value
Define ‘average’.
mathematical middle value
Temporal refers to…
all time, transmit (pulse duration), and receive.
Pulsed refers to…
transmit time only (ignoring listening time).
What is spatial peak intensity?
The beam’s intensity at the location where it is at its maximum; I-sp
What is spatial average intensity?
The average intensity across the beam’s entire cross-sectional area; I-sa
Spatial peak intensity is always ___ than the spatial average intensity.
higher
What is temporal peak intensity?
The intensity of the beam at the instant in time of its maximal value; I-tp
What is maximum intensity?
The average intensity during the most intense half-cycle; I-max or I-m
What is pulse average intensity?
The average intensity during the pulse duration (transmit only); I-pa
What is the temporal average intensity?
The average intensity during the entire pulse repetition period (transmit + receive); I-ta
Of the four temporal intensity measurements, which has the highest value?
temporal peak (I-tp) which is slightly higher than I-max.
Which is the lowest of the temporal intensity measurements?
temporal average (I-ta)
Temporal intensities from largest to smallest?
I-tp, I-max, I-pa, I-ta
Which intensity is measured at the location where intensity is maximum and at the instant in time when the most powerful part of the pulse passes?
I-sptp
Which intensity is measured at the location where intensity is maximum, averaged over the pulse duration?
I-sppa
Which intensity is measured at the location where intensity is maximum and averaged over all time?
I-spta
Which intensity is measured over the entire cross-sectional area of the sound beam and over all time?
I-sata
Intensities may be reported in various ways with respect to…
time and space.
The different measurements of intensities are important in…
the study of bioeffects.
Which is the most relevant intensity with respect to tisue heating?
I-spta
Intensities are reported in units of…
W/cm^2
Peak measurements are ___ than average measurements.
larger
Which intensity has the highest value?
I-sptp
Which intensity has the lowest value?
I-sata
What number describes the spread of a beam in space?
the beam uniformity coefficient (aka SP/SA factor)
The beam uniformity coefficient (SP/SA factor) is reported in units of…
Trick question! It’s unitless, with a value of 1 or greater.
What describes the relationship of beam intensities with time?
The duty factor
The duty factor is reported in units of…
Trick question! It’s unitless, with a value between 0 and 1.
In continuous wave u/s the pulse average and temporal average are the ___.
same. So SPTA = SPPA and SATA = SAPA.
When pulsed and continuous wave sound beams have the same SPTP intensities, the continuous wave beam has the ___ SPTA intensity.
higher
When pulse and continous wave sound beams have the same SATP intensities, the continuous wave beam has the ___ SATA intensity.
higher
I-tp is the ___ intensity in time.
maximum
I-m intensity is averaged over the most intense ___.
half-cycle
I-pa is averaged during the ___.
pulse duration
I-ta is averaged during the ___.
pulse repetition period
I-sp is the ___ in space.
maximum
I-sa is averaged over the ___.
cross-sectional area of the beam
Rank the intensities from largest to smallest.
SPTP, I-m, SPPA, SPTA, SATA
